RADIATION PHYSICS CORE (RPC) PROJECT SUMMARY Animal models are essential to test the efficacy of medical countermeasures against radiation. Efficacy is quantified at a specified level of tissue damage or animal death by the dose modification as a result of mitigation. This requires accurate delivery of the same radiation dose to the same tissue volume across participating centers. Unlike human radiotherapy that is rigorously monitored by professional medical physicists on a routine basis following a national standard, the dosimetric accuracy and reproducibility for preclinical radiation experiments are crude due to the lack of standard quality assurance protocols, prohibitive cost associated with rigorous QA programs, outdated equipment and different endpoints that may not be well defined. These limitations have resulted in unknown radiation dosimetry accuracies in previous preclinical radiobiology experiments, which may be acceptable when the dose was interpreted on a relative scale. However, the lack of a standard quality protocol is unacceptable to CMCRC that aims to compare the efficacy of chemical compounds developed at different centers on an absolute dosimetric scale. Although a national standard in small animal dosimetry is impractical, we believe that a radiation physics core can be established for the CMCRC. We aim to achieve consistent radiation dosimetry for the participating centers so the radiation protection efficacy of chemical compounds developed by different labs can be compared on the same scale. To achieve this goal, we propose the following aim. 1. Education. Since most operators of the small animal irradiator are not medical physicists and do not have previous training in dosimetry, it is imperative for them to understand the factors contributing to inaccurate dosimetry and be able to follow the standard quality assurance protocols designated by the RPC. We will provide remote and online seminars to disseminate such information and be available for individual question and answers. 2. Establish SOPs and QA procedures. We propose to develop cost effective QA procedures that can be performed by individuals with minimal equipment and training at each participating center with remote RPC technical support. The QA procedures will be individualized to three main types of irradiators used by the Consortium: Cs-137, Co-60 and orthovoltage X- rays. 3. Service. We realize that certain measurements are still difficult without medical physics training and dedicated equipment. We will provide onsite initial QA for each machine that will be used for the consortium. We will establish a baseline for subsequent annual and monthly QA that will be performed by onsite personnel. We will provide consultation services for special physics dosimetry that cannot be achieved using open field radiation. We will make phantoms for QA tests and perform remote QA by mail. Success of the project will not only ensure the quantification and reproducibility of animal models and effects of compounds to countermeasure radiation effects, it will set an example for potential wider adoption of a model system for overall improvement of radiobiology dosimetry.